I had this problem in my earlier car and the new car I am using now. I was wondering why this happens in a new car. All my internet searches lead me many things not worked for me.
Things did NOT work for me are:
1. Vinegar Treatment
2. Lime scale remover
3. Glass cleaner
5. All highly priced branded car windshield cleaners
6. Lime Juice
what not...Nothing worked.
Some said like use a clay bar...blah, blah....
But the solution is simple and here it is
Just wash your wind shield with DISH WASHER SOLUTION. I live in Chennai, I used Vim Solution, But then it shall be the case every good dish washer solution out there in the grocery shop. Just use about 20 drops of dish washer solution, spray little water, rub it with a cloth or hands to lather and wipe of. Then wash and wipe with water.
In my understanding, the Tar / residual hydrocarbons from the vehicle exhaust get deposited on the wind shield and form a thin sticky film that causes smudge when wiped by the wipers. Don't waste your money buying highly priced car items sold in the Petrol Bunks, car accessory shops etc, I found them simply useless.
If you find spotted smudges, may be you could shave them off with a new shaving blade (INR 10 approx) or you can resort lime scale remover solutions.